Bellmouth intake design

Submitted by Anonymous on

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From: <adam [at] validationpartners.com>
Sender: <marv [at] lancaironline.net>
Subject: Bellmouth intake design
Date: Tue, 09 Sep 2014 07:43:33 -0400
To: <lml [at] lancaironline.net>

I currently have a simple wire screen over my throttle body. Intake air is drawn from the high-pressure cooling air in the engine plenum. However I recently read that a straight intake pipe which draws air without the benefit of ram pressure is inefficient. Some air gets drawn in from the sides and has to make a sharp 90-degree bend. This results in a ring of low pressure air which "chokes" the intake somewhat.



Hot rodders have long understood the benefit of smoothing the intake air using a bellmouth inlet (sometimes called a velocity stack). Bellmouths are also installed on jet engines when they are run in a test stand (see attached photo).



So my question is, can someone point me to any drawings or papers which spell out the optimum shape for a bellmouth? Just has we have specifications for NACA scoops and airfoils I imagine someone did the research for air intakes.



Once I have a CAD drawing on hand, this seems like a good candidate for 3-D printing.



Thanks,

Adam Molny

Legacy N181AM, 295hrs

Bellmouth intake design

Submitted by Anonymous on

From: <marv [at] lancair.net>
Subject: Re: [LML] Bellmouth intake design
Date: Tue, 09 Sep 2014 09:45:22 -0400
To: <lml>
Message Header


Undecoded Message

Posted for "Bill Harrelson"
<n5zq [at] verizon.net>:

 Adam,

 I too obtain my induction air from the engine plenum.  I believe that
tapping
the high pressure environment above the engine is better than tapping
the high speed environment of a ram tube. I use a conical K&N filter.
Not
seen in the photos are carbon baffles that surround the air filter from the
front and prevent any air from entering the filter directly
from the intakes.
 This deflects ice, bugs and debris that might otherwise be able to get to
the filter. With the baffles, air must enter
the filter from behind.  I get
substantial manifold pressure rise with IAS increase and the filter remains
mostly
clean.

 Bill Harrelson
 N6ZQ  IV  600 hrs





> -----Original Message----- From:
adam [at] validationpartners.com
> Sent: Tuesday, September 09, 2014 7:43 AM
> To: Lancair Mailing List
> Subject: [LML] Bellmouth intake
design
>
> I currently have a simple wire screen over my throttle body. Intake air
> is drawn from the high-pressure cooling air in
the engine plenum.
> However I recently read that a straight intake pipe which draws air
> without the benefit of ram pressure is
inefficient. Some air gets drawn
> in from the sides and has to make a sharp 90-degree bend. This results
> in a ring of low pressure air
which "chokes" the intake somewhat.
>
> Hot rodders have long understood the benefit of smoothing the intake air
> using a
bellmouth inlet (sometimes called a velocity stack). Bellmouths
> are also installed on jet engines when they are run in a test stand
(see
> attached photo).
>
> So my question is, can someone point me to any drawings or papers which
> spell out the optimum
shape for a bellmouth? Just has we have
> specifications for NACA scoops and airfoils I imagine someone did the
> research for air
intakes.
>
> Once I have a CAD drawing on hand, this seems like a good candidate for
> 3-D printing.
>
>
Thanks,
> Adam Molny
> Legacy N181AM, 295hrs
>
>
>
>
>
>
> --
>For archives and
unsub http://mail.lancaironline.net:81/lists/lml/List.html

Bellmouth intake design

Submitted by Anonymous on

From: Brent Regan <brent [at] regandesigns.com>
Subject: Re: Bellmouth intake design
Date: Tue, 09 Sep 2014 07:23:45 -0700
To: Lancair Mailing List <lml [at] lancaironline.net>
Message Header


Undecoded Message

Adam asks "can someone point me to any drawings or papers which spell out the optimum shape for a bellmouth? Just has we have specifications for NACA scoops and airfoils I imagine someone did the research for air intakes."



There is an optimal design for ducted fan inlets (turbofan engines) because the duct inlet contributes about a quarter of the total engine thrust. The engine is accelerating air over a curved shape, just like what happens with the wing.



Induction air inlets are not as sensitive as all you are trying to do is maximize the diameter of the vena contracta and to do that all you need is a nice fat radius, say about a quarter the inlet tube radius. So for a 3" diameter, use a 3/8" radius minimum.



Brent Regan